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dthompson
01-26-2017, 09:50 PM
Im looking for ideas to help trouble shoot what I now believe to be a clutch problem. For a while now, I have experienced a problem in the following scenario: The engine is cold, I press in the clutch and start the car, put the car in rev, back out of the garage, release the clutch and then let the car warm up in the drive way in neutral with the clutch out. I let the car partially warm up for a few minutes, then push the clutch in and try to put it in 1st, but its like im blocked out of the gear... i try all the other gears and its the same thing. pumping the clutch a dozen times makes no difference. if i push hard enough, it will eventually go into gear. or if i shut the engine off (while still holding the clutch in, it will fall into gear as soon as the engine stops spinning. i can easily shift into all gears while the engine is off. Otherwise the car drives perfectly fine. shifts fine while you are rolling and normal driving.

What I am working with: Stock resurfaced flywheel (89 sc), Centerforce DF clutch with about 4k miles, aftermarket replacement slave cylinder (centric brand i think), aftermarket replacement hydraulic line, and stock original master cylinder.

These are the things that i have tried and/or tested:

Ive replaced blockers with Mike Pucket's CF blockers and tried all kinds of fluids. I thought maybe it was a fluid problem with the blockers that i just could not get right, so i pulled the trans and replaced the blockers with solid brass blockers. i still have the same problem.

I have replaced the pilot bearing. Same problem.

I inspected the clutch flywheel and PP. there are some slight discolored spots on the PP. I held a straight edge across the mounting surface of the PP and measured down to the friction surface using calipers and it seemed to be parallel within a few thousandths everywhere a checked. I held a straight edge across the friction surface of the PP and it seemed flat except for one spot that i could fit a 0.006" feeler gauge under the straight edge. The clutch disk looked ok to me, i did not see anything physically wrong with the springs and the splines moved easily on the input shaft. The flywheel seemed flat and parallel to the transmission mating surface of the block using using the same method of measurements described in checking the PP.

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I used my cell phone to capture video of the slave cylinder pushing on the PP to verify that the hydraulic system was working visually. The slave seems to be traveling 3/4" it looks like to me. The clutch disengages near the top of the pedal, so it seems to me that the hydraulic system is functioning properly. I repaired the clutch pedal linkage recently securing the piston rod to the pedal using a shoulder bolt.


https://www.youtube.com/watch?v=UQ_UXzuu5HU&feature=youtu.be

So that is where I am at right now. It seems like the input shaft is spinning which may be causing this problem, but i dont know how to prove it. I feel like I am stuck other than throwing parts at it which is now going to be expensive. If anyone has suggestions on what to try, test, measure, or replace... I am all ears. New flywheels and clutches are expensive, so if thats what I need, then I want to make sure I diagnose it properly. Plus every time i have to pull this trans out, I am rolling around on the concrete which is taking a toll on my body.

Thanks,
Derek

dthompson
01-26-2017, 09:51 PM
more pictures of flywheel and input shaft.

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the arrows on the input shaft are highlighting shiny areas on the splines where you can see the disk was sliding.

Thanks,
Derek

KMT
01-26-2017, 11:14 PM
I see:


Stock resurfaced flywheel (89 sc)

...but I don't see the word 'shim' anywhere?

sam jones
01-26-2017, 11:19 PM
Good evening


I experience the similar symptoms. The problem deteriorated to the point I would have the car start and idle for at least 40 minutes before I could get the transmission to engage in reverse and


first. I ordered a clutch kit, the shifter rebuild kit, the clutch peddle bushing, the master and the clutch line. After adding friction modifier, ATF change and clutch bleed the transmission shifted


great with the exception of first gear because of all the "hulk smash" I did to put it in gear. I suspect the problem might be a leaking master and or clutch line issue if there is not issue


with the flywheel machined limits.



Good Luck.

dthompson
01-26-2017, 11:30 PM
I see:

...but I don't see the word 'shim' anywhere?

i have not removed the flywheel to see if they shimmed behind it? The engine builder installed the flywheel and the clutch when i had it built. there are no shims behind the slave.

I'm guessing that you are getting at the idea the clutch is too far away from the flywheel because it was resurfaced and therefore not pressing on the clutch enough to release it fully. My assumption is that the slave is moving enough to disengage the clutch because the clutch engages at top of the pedal travel. I would say it engages at .75" of pedal travel if the overall pedal travel is ~3". also combining this with the video, this doesnt seem like the problem to me. But I could be wrong, Im not a mechanic. I've still got a lot to learn.

KMT
01-26-2017, 11:40 PM
Measured the distance on that install from the block mounting surface to the face of the friction surface on the flywheel yet?

I'll try to find the spec - apparently it doesn't take much to cause grief. Maybe as little as a thousandth inch...

sam jones
01-27-2017, 03:23 AM
Good morning

Post#1 picture attachment #2 and Post #2 picture attachment #1 the pilot bearing does not look fully installed. Maybe angle of the camera?

TbirdSCFan
01-27-2017, 04:00 AM
Good morning

Post#1 picture attachment #2 and Post #2 picture attachment #1 the pilot bearing does not look fully installed. Maybe angle of the camera? Wow.. good catch.

dthompson
01-27-2017, 07:58 AM
Good morning

Post#1 picture attachment #2 and Post #2 picture attachment #1 the pilot bearing does not look fully installed. Maybe angle of the camera?

I think it is installed correctly. the pilot is comprised of an outer bushing and an inner needle bearing. the outer bushing is installed flush and the need bearing protrudes about 0.1". I used a national bearing brand, but this is a picture of the timken brand. Also notice the witness marks on the input shaft. their are no marks on near where the splines begin.

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XR7 Dave
01-27-2017, 12:52 PM
It's a bad clutch disc. Last time I'm going to say this. :)

dthompson
01-27-2017, 12:55 PM
Thanks Dave. How do I check it to prove that it is bad other than swap and test?

XR7 Dave
01-27-2017, 05:36 PM
Thanks Dave. How do I check it to prove that it is bad other than swap and test? I don't think you could really do a reliable test/check. But your symptoms are 99% bad disc. Since everything else is good, I'd just order a new disc.

XR7 Dave
01-27-2017, 05:51 PM
I mean, of course I'm qualifying this with the understanding that the system is properly bled and the pedal pin engagement is correct such that your pedal free play is within spec and that the clutch is engaging within a reasonable range of the middle of pedal travel. These are mechanical adjustments/parameters that are assumed to be correct at this point.

dthompson
01-27-2017, 08:31 PM
I mean, of course I'm qualifying this with the understanding that the system is properly bled and the pedal pin engagement is correct such that your pedal free play is within spec and that the clutch is engaging within a reasonable range of the middle of pedal travel. These are mechanical adjustments/parameters that are assumed to be correct at this point.

It feels like it is bled correctly, the pedal feels pretty firm and consistent as you push it. the clutch pedal pin has been replaced by a shoulder bolt and bronze bushing. I have no idea what the free play spec is, but I would describe it as very little. I would describe the clutch engagement as within the top 25% of pedal travel. I made this video tonight to show you just in case I'm not describing it correctly.

showing how I modified the clutch pedal attachment
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video showing free play and clutch engagement. if you turn the volume up enough you can hear the engine load as the clutch engages at the same time I say "engaging". lol you can also hear me grunt as i try to put it back into first gear!

https://www.youtube.com/watch?v=9kxToU3X43c&feature=youtu.be

Thanks,
Derek

dthompson
01-27-2017, 10:37 PM
I could not find a spec on flywheel thickness. The only thing i found was that you need to use a new flywheel if you have to machine more than 0.045" off of it. that is not particular helpful if you dont know where it started. I assume that as long as it is not running out it is ok since the clutch engages so high on the pedal.

I also bought a dial gauge and magnetic base today. I will be able to check fly wheel run out and to see if the input shaft is bent/runout.

Is there a spec for flywheel runout? i did not see that in the shop manual.

sam jones
01-27-2017, 11:35 PM
Good evening


Maybe this will help: http://www.sccoa.com/forums/showthread.php?18838-This-is-NOT-looking-good

davec73
01-27-2017, 11:46 PM
I got my flywheel from Mike puckett. He gave me the thickness of the flywheel but all mine needed was a shim between the crank and flywheel.

KMT
01-28-2017, 12:20 AM
I could not find a spec on flywheel thickness.

Other thread here [ http://www.sccoa.com/forums/showthread.php?47888-Shifting-Trouble-!!!!!&p=308720#post308720 ] claims 0.99" factory.

dthompson
01-28-2017, 06:23 PM
I measured the flywheel thickness this afternoon. It measures 0.962" thick

I need to check the runout again. My setup was not rigid enough and the video was not clear (i cant see dial while I turn the crank). It looks like it was less than the 0.007" listed in the other thread... if that really is the spec.

dthompson
01-29-2017, 04:29 PM
The flywheel runout is less than 0.001"

I set the dial gauge up on the input shaft and im not sure if its bent or if is just a result of the tapered bearings. It runs out about 0.015" and wiggling it by hand it looks like 0.020"-0.030" depending on force. If I had to guess, I would think this is normal given the bearing structure. Its not going to move like this when it is in the pilot bearing. But I will post it and you guys can correct me if I am wrong. Check out the video (i apologize for the poor lighting and video quality)...


https://www.youtube.com/watch?v=2rLtBMvjUzo&feature=youtu.be

The transmission was rebuilt using all original factory parts except the blockers, seals, main and countershaft nuts, and tailshaft bushing. No shims were added to the input shaft. The last time i had it apart i checked the dimensions per the service manual and it is super close to the correct tolerance on the input shaft shim. Although that stuff is somewhat tricky to measure.

Thanks,
Derek

XR7 Dave
01-29-2017, 08:49 PM
It's fine, replace the clutch disc.

[edit] Damn, I said it again. lol sorry

dthompson
01-29-2017, 09:04 PM
It's fine, replace the clutch disc.

[edit] Damn, I said it again. lol sorry

Fine, you win... LOL. :) It will be here Wednesday.

dthompson
01-29-2017, 09:46 PM
would it be a good idea to add a 0.030 shim behind the slave? You know, while i was in there?

TbirdSCFan
01-29-2017, 11:27 PM
It's fine, replace the clutch disc.

[edit] Damn, I said it again. lol sorry Sounds like me, on an unrelated topic, with "check your engine mounts.. and no I'm not joking!" over allll the years.. its disbelief until they find out their problem was the mounts. That is until the NEXT one comes along ;)

On the actual related topic, FWIW, I can state that I haven't had any problems with a stage 2 clutch, CF blockers, and using GM syncromesh fluid.

davec73
01-30-2017, 12:55 AM
would it be a good idea to add a 0.030 shim behind the slave? You know, while i was in there?I would but you would be better off putting one between the crank and flywheel. That's how mine was.

KMT
01-30-2017, 01:06 AM
...but you would be better off putting one between the crank and flywheel.

Circling back to my shim question on the 26th, I second that idea. Might even save the expense of another disc, especially when the one that came out only has 4k on it so far.

XR7 Dave
01-30-2017, 09:31 AM
If you consider the physics involved, installing a shim will have no impact on the result in this case.

dthompson
01-31-2017, 11:46 PM
Is it recommended to lubricate the splines of the input shaft? the manual says something like a lithium grease. Ive done it with grease and without. Im always afraid of that crap getting on the clutch surfaces. What do you guys use?

The disk will be here Wed, so hopefully i can slam it back together tomorrow night.

davec73
02-01-2017, 01:00 AM
Is it recommended to lubricate the splines of the input shaft? the manual says something like a lithium grease. Ive done it with grease and without. Im always afraid of that crap getting on the clutch surfaces. What do you guys use?

The disk will be here Wed, so hopefully i can slam it back together tomorrow night.
Only with a dry lube. Anything else will get all over everything.

neverfastenough
02-01-2017, 08:31 AM
Is it recommended to lubricate the splines of the input shaft? the manual says something like a lithium grease. Ive done it with grease and without. Im always afraid of that crap getting on the clutch surfaces. What do you guys use?

The disk will be here Wed, so hopefully i can slam it back together tomorrow night.

Over multiple transmissions, multiples disks, I've never lubricated the splines.

KMT
02-01-2017, 12:02 PM
I like the pointers in this 2004 comment...

http://www.sccoa.com/forums/showthread.php?73485-Tranny-shim-questions

And 2006:
http://www.sccoa.com/forums/showthread.php?73485-Tranny-shim-questions&p=498541#post498541

And 2013:

http://www.sccoa.com/forums/showthread.php?130743-Centerforce-clutch&p=1040467#post1040467

Can't imagine what to do if both a new disc and shims don't cure the problem, but if both are done at the same time there would be no way to know if only one was actually needed, so... ;)

Good luck in any case.

Ken

dthompson
02-05-2017, 06:26 PM
I got the new disk installed Thursday night, but had some trouble getting the transmission back in... Friday I bought a harbor freight trans jack (looks like a scissor lift) and it worked great. Im not a big harbor freight fan, but that was money well spent. The trans went back in easier than ever before. While I had the transmission out, I tore it apart and put Mike Pucketts CF 1-4 blockers back in and used the solid brass Cobra transmission 5-R blockers. I filled the trans with 3 quarts of ACDelco 10-4006 Synchromesh Manual Transmission Fluid and one 4oz bottle of Motorcraft XL3 Friction Modifier.

Ive driven the car about 70 miles now. 3 completely cold starts, probably a dozen stops, and who knows how many stop lights without a problem.

Looking at the old disk, there is not an obvious problem... at least one that I can see. Thinking back on things, when the motor was built, the clutch was installed brand new. The car had maybe 1 mile on it before it hit the dyno for tuning. So the brand new clutch got repeated full power pulls without any real break in. Maybe this was the cause, because this issue has been a problem for 4 years, ever since I got the car running again. The problem became more pronounced once I installed the B&M short throw shifter. So, a big Thank You to David for his advice on this one. Its really nice to drive the car, without having to fight it into gear. Its like it should be now.

In case anyone ever needs the part number for the Centerforce Dual Friction Disk... its part number DF281226

KMT
02-05-2017, 07:17 PM
Good job - thanks for the update.

aroot1
02-06-2017, 06:54 PM
"David was right"

Rule #1 David is ALWAYS right......

Rule #2 when in doubt, see rule #1....

:D:p:D:p

LOL!!!

Been my experience with the man any way

Adam